Lecture 9: Animal Communication - Tube Map Central · Lecture 9: Animal Communication • 9.1 What is Communication? • The language debate • Communication and intelligence •

Maxwell J RobertsDepartment of Psychology

University of Essexwww.tubemapcentral.com

version date: 19/11/2019

PS452Intelligent Behaviour

Lecture 9:Animal Communication

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Part 3: Intelligent Behaviour in Animals

• Lecture 7: Animal Intelligence TestsMeasuring animal cognitive capacity

• Learning and logic between species

• The ubiquitous g factor

• Lecture 8: Tools, Puzzles, Beliefs, and IntentionsComplex interactions with objects

• Natural tool use

• Understanding the properties of objects

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Part 3: Intelligent Behaviour in Animals

• Lecture 9: Animal CommunicationMindless signals or deliberate acts

• Natural communication

• Taught language in the laboratory

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Lecture 9: Animal Communication

• 9.1 What is Communication?

• The language debate

• Communication and intelligence

• 9.2 Natural Animal Communication

• Bees (and ants)

• Vervet monkey alarm calls

• Limits to natural communication

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Lecture 9: Animal Communication

• 9.3 Taught Animal Language

• The ape sign language projects

• The ape artificial language projects

• Language or problem solving training?

• Postscript: teaching other animals language

• 9.4 What Does Communication Reveal?

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9.1 What is Communication?

• General definition: communication is …

• A signal emitted by an animal, containing information,that may influence the behaviour of others

• Appearance, (markings, gesture, posture), sounds, smell, touch, taste all implicated

➡ Human language = specialist communication method

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The Language Debate

• Human language has at least all of the following (e.g., Aitchison, 1989; Pearce, 2008):

• Arbitrary symbols

• Semanticity/reference (meaning)

• Displacement (in time, space)

• Productivity (discrete units in combination)

➡ How unique is this?

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The Language Debate

• Do (can) any animals have (learn) language?

• Impinges on massively entrenched ideologies

• Nativists (language = genetic predisposition?)

• Behaviourists (language = lucky accident?)

• Philosophy (language = marker of thought?)

• Animal rights (language = marker of affinity?)

➡ Bad question: leads to endless futile debate

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Communication and Intelligence

• Language use requires cognitive capacity

‣ Most humans can learn to use languageirrespective of cognitive capacity

‣ But low intelligence associated withless effective use (Gottfredson, 2007)

➡ Understanding/producing word strings whose meaning depends upon order is demanding of cognitive capacity

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• Language use enhances cognitive capacity

‣ Meo, Roberts & Marucci (2007): Matrix itemswith readily verbalisable elements are easier

➡ Language can enhance cognitive capacityby permitting economical representations

➡ Also, language enhances organised structured thinking

➡ Language possession has cognitive FRINGE BENEFITS

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• Animals triply penalised?

• Complex communication

• Harder to learn

• Harder to use

• Capacity enhancement harder to achieve

• Less able to learn language because oflower cognitive capacity than humans

• Less able to attain cognitive FRINGEBENEFITS of mastering a language

➡ Language widens cognitive capacitygulf between animals and humans

➡ Likewise gulf in associated mental achievements

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• What aspects of animal communication will providethe best markers for intelligent behaviour?

• Intentional communication

• Deliberate acts that implyknowledge of others’ mental states

• Complex communication

• Learning/use that would require high cognitive capacity,e.g. sequencing, as demonstrated by grammar and nesting

• High-level concepts such as symbol and meaning

• Evidence for beginnings of fringe benefits

• What has developed naturally?

• What can be achieved with assistance?

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9.2 Natural Animal Communication

• No point developing sophisticatedcommunication system just to talk to oneself

➡ Target investigation on social animals

• See Aitchison (1989), Pearce (2008),Reznikova (2007), Seyfarth & Cheney (2003)

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• Non-symbolic communication

• Animals infer a great deal from gesture(e.g. gaze direction, body movements)

➡ But output not necessarily intentional

• Some animals appear able to use gestures to deceive

➡ Non-symbolic deception investigated in Lecture 10

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• Symbolic communication

• Some communication can be interpreted ascomprising arbitrary signals, e.g., calls and songs

“My territory: go away”

“Excellent food here”

“Flying predator approaching”

➡ But computer use of symbols is insufficient for intelligence

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• Computer communication

• Most effective (and convincing) withinhighly constrained micro worlds

• But unintelligent procedures, zero understanding

• What would be necessary for computersto demonstrate intelligence

• Adaptability of communication to unusual circumstances

• Evidence of understanding of the meaning of their output

➡ Same criteria necessary for animals to demonstratethat communication reflects underlying intelligence?

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Bees (and Ants)

• Foraging recruitment in bees takes placewhen plentiful food sources located

(1) Bee finds nectar source

(2) Bee returns to the hive and initiates special movements

(3) If sufficiently motivated, the recruited bees fly to location

• Excellent spatial abilities: can signal adirect route even when not originally taken

• Nearby food

• Simple circular dance

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Bees (and Ants)

• Distant food (over 100m)

• Wagging dance (figure 8-shaped)

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Bees (and Ants)

• Distant food (over 100m)

• Wagging dance (figure 8-shaped)

• Distance from food = length of middle section

• Direction of food = orientation of middlesection in relation to the sun/hive

• Food quality = provided by samples

• Wing sounds enhance urgency

➡ Communication is displaced and symbolic19

Bees (and Ants)

• No evidence for bee adaptability or understanding

(1) von Frisch

• Food source placed several yards in the air

• Bees released at source returned to hive, performed dance

‣ Other bees searched for several hours, could not find food

➡ Cannot communicate height, or devise method for this

➡ Do not know that they cannot communicate height

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Bees (and Ants)

• No evidence for bee adaptability or understanding cont.

(2) Dyer

• Food source was moored in the centre of a river

‣ Bees failed to recruit others to collect it

➡ Bees rejected possibility of food in river = intelligent

➡ But signalling bees were unable to circumvent this

(3) Riley

• Recruited bees leaving hive were captured and displaced

‣ Bees did not modify journey, did not find food

➡ Spatial abilities of bees previously over-estimated

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Bees (and Ants)

• No evidence for bee adaptability or understanding cont.

• Bees cannot communicate some concepts

• Bees do not know that they cannotcommunicate these concepts

➡ Performance is brittle

➡ Bees occupy a natural micro-world

• Excellent performance a typical situation

• Errors in unusual situations imply limited understanding?

‣ Simple genetic links to individual dance elements

➡ Bees are effectively natural computers

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Bees (and Ants)

• Reznikova (2007)

• Ants communicate via antenna

‣ Routes to obtain food, complex routes = longer ‘messages’

‣ Can develop communication short-cuts using key landmarks

➡ Ants communication more sophisticated than bees?

➡ Better communication capability than many mammals

• Too early to determine level of ant communication adaptability and understanding

• Could communication be modified toaccount for unusual circumstances?

➡ In the interim, safest to conclude ant brainprocesses equivalent to bees/computers

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Vervet Monkey Alarm Calls

• Vervet Monkeys emit a wide variety of sounds

• Some of these are alarm calls

chutter: puff adder/cobra rraup: eagle chirp: lion/leoparduh: hyena/human

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• Seyfarth, Cheney & Marler (1980)

‣ When a call is made, others repeatit and respond appropriately

‣ chutter (for snake): stand on hind-legs, look around rraup (for eagle): dive into undergrowth chirp (for lion): climb a tree

‣ Taped calls lead to similar behaviour as vocalisedones, no need to see predator or caller

‣ Changing volume and duration of taped callshas no effect on strength of response

➡ Calls indicate type rather than intensity of danger

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• Seyfarth, Cheney & Marler (1980) cont.

‣ Second call, or appearance of predator doesnot lead to further repetitions of the call

➡ Further calls would not be adding newinformation in these instances, so not made

➡ Calls have meaning and display intentionality?

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• Cheney & Seyfarth (1985, 1991)

• Varied vervet monkey company and its (visible) status

‣ Mother more likely to give an alarm call whenown offspring present than other young

➡ NOT Zero Order intentionality (not a reflex)

‣ No relationship to knowledge of target(agent knows this via target gaze direction)

Target cannot see danger: receives alarm callTarget can see danger: receives alarm call

➡ NOT 2nd Order intentionality (unrelated to target’s beliefs)

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• Seyfarth & Cheney (1993, See Pearce)

• Other species of ape threaten infants,only infants make baboon alarm call

• Threatening ape hidden in enclosure in full view of mother

‣ Young vervet monkey entered, mother failed to give warning

➡ Mother failed to understand situation,failed to display adaptability to unusual situation

➡ Vervet communication:1st Order intentionality at the very best, aware of other monkeys, but not their mental states

➡ Arguments against even 1st Order (Burghardt, 1985)

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Limits to Natural Communication

• Many animals have contextual calls

Diana monkeys (different threats)Macaques (different types of food)Chickens (aerial versus ground predators)Prairie dogs (different predators)Meercats (different predators)

• Many animal calls show audience effects

ChickensGround squirrelsJungle fowl

➡ In all cases, same problems to answering key questions:

Do calls have meaning?Do calls indicate intentionality?

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• Cheney & Seyfarth (1992)

• Precise definitions are possible for humanlanguage because we have many words

➡ Even if Vervet calls have meanings,hard to pin these down

Would ‘lion’ warning still be given if no trees present?

• Seyfarth & Cheney (2003)

• Communication and intentionality limited because animals cannot attribute mental states to others

➡ Others’ beliefs unknown, so cannot try to change them

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• Pearce (2008)

➡ No animals interact with sufficient complexity toimply anything equivalent to human language

[Not even dolphins, insufficient space for this topic]

• Language has biological and developmental ‘baggage’

➡ No animals interact with sufficient complexity toneed anything equivalent to human language

➡ Simple signals suffice in vast majority of circumstances

➡ Natural communication reveals no hidden capacity for intelligent behavour not already revealed in Lectures 7/8

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9.3 Taught Animal Language

• Natural communication difficult to study

• Lack of control of acquisition

• Unclear meanings of utterances

➡ Is it possible to teach animals communicationmethods that will avoid these problems?

➡ For example, can primates be taught human-like grammatical language and display understanding?

• Aitchison (1989), Pearce (2008), Pinker (1994),Reznikova (2007), Wallman (1992)

• Caution: entrenched ideologies and vested interests zone

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The Ape Sign Language Projects

• Behaviourism roots

• Any animal can learn language if correct reinforcement

• Humans lucky, stumbled on language by accident?

• Initial projects simply tried to bring up chimpanzees in human surroundings, no language learning

• Attempts to teach chimpanzees vocalisations also failed (physically impossible)

➡ Apes very dexterous, teach them sign language?

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• Washoe – Chimpanzee (Gardner & Gardner, 1969)

• Teaching

• Surrounded by humans signing

• Intention: signs acquired by observation/imitation; failed

• Shaping ineffective, moulding eventually preferred method

• Vocabulary

‣ Learnt over 30 signs in 21 months

‣ 130 in four years until project ended

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• Washoe – Chimpanzee (Gardner & Gardner, 1969) cont.

• Combination

‣ Two/three sign combinations frequent,

GIMME TICKLEGO SWEET (take to raspberry bushes)OPEN FOOD DRINK (open refrigerator)

• Grammar

‣ Little evidence for learning importance of word order,but not given rigorous training

GO SWEET = SWEET GO

‣ Claimed that word order became more regularwith time, reached level of a human 2 year old

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• Washoe – Chimpanzee (Gardner & Gardner, 1969) cont.

• Understanding and inference

‣ Able to give correct (noun) sign when shown slides

‣ Generalised: MORE initially used when being tickled,then used in context of other games and food

‣ Overgeneralised: FLOWER anything with a strong smell

• Culture

‣ Education: Evidence of teaching signs to other chimpanzees after training program ended

➡ Clear evidence for human-like languagedevelopment and production?

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• Koko – Gorilla (Patterson)

• Vocabulary

‣ Over 600 signs claimed

• Combination

‣ Longest sequence

PLEASE MILK PLEASE ME LIKE DRINK APPLE BOTTLE

• Grammar

‣ No claims for grammatical structure

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• Koko – Gorilla (Patterson) cont.


‣ Creativity: combined signs if appropriate one not taught

EYE HAT (mask)WHITE TIGER (zebra)COOKIE ROCK (stale roll)

‣ Higher order: claims for metaphors, puns, insults, lies

signed RED FROG for frog [an error, surely?]

➡ Koko is claimed to have an IQ of 85-95

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• Nim Chimpsky – Chimpanzee (Terrace, 1969)

• TeachingVocabulary

• Similar to Washoe

• Combination

‣ Plenty of multi-sign combinations, longest one 16 words

GIVE ORANGE ME GIVE EAT ORANGEME EAT ORANGE GIVE ME EAT ORANGEGIVE ME YOU

➡ Additional signs are for emphasis not extra information

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• Nim Chimpsky – Chimpanzee (Terrace, 1969) cont.

• Grammar

‣ Word order was statistical rather than rule driven

MORE first word 78% of useTransitive verbs before object 83% of use

‣ Some words had position preference, others had none

EAT NIMMORE EATME EATEAT DRINK

➡ Individual word instances learnt rather than category rules

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• Nim Chimpsky – Chimpanzee (Terrace, 1969) cont.


‣ Proportion of signs that were imitations increased with time

➡ Language being adopted for obtaining food and gratification, learnt that imitation was a useful strategy

➡ Despite initial support, Terrace skeptical of claims thatapes are able to learn language in the human sense

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• Interim evaluation: Sign language

• Seidenburg & Petitto (1979)

• Skilled users of sign language complain:

• Apes did not adhere to conventions,were not trained and observed by skilled users

• Many of the counted signs are naturalgestures (e.g. scratch, hug)

➡ Overestimated quantity of learned signs

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• Interim evaluation: Sign language cont.

• Sebeok & Umiker-Sebeok (1980)

• Many studies badly implemented

• Unintended cues by experimenters

• Understanding versus accidents/researcher bias?

➡ Anecdotal evidence cannot offer any conclusions about language learning ability, data/analysis needed

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• Interim evaluation: Sign language cont.

• Why the emphasis on can apes learn grammar?

• Cornerstone of a futile debate

• Chomsky: humans uniquely programmed forlanguage, have an innate ability to learn grammar

• Opponents: if apes can learn language, no special innateness necessary to account for human language

• Useful for understanding animal intelligent behaviour

• Sequential changes to word order affect meaning

• Demanding of cognitive capacity to recognise, learn, use (compare with animal intelligence tests, Lecture 7)

➡ Apes learnt to solve (some) problems, but grammarlearning is at the limits of available cognitive capacity

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The Ape Artificial Language Projects

• Apes learn sign language with difficulty

• Meaning/origin of gestures problematic

• Ape ability to learn grammar inconclusive

➡ American Sign Language too ’organic’?

• Lack of systematicity makes signs harder to learn?

• Does not support grammar learning well?

• A more constrained and regular language is necessary?

➡ Teach apes artificial language expressedusing symbol tiles or a keyboard?

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• Sarah – Chimpanzee (Premack, 1971)

• Teaching

• Taught to manipulate magnetic tokens,varied in colour and shape

MAUVE TRIANGLE = appleBLACK T-SHAPE = the colour yellow

• Shaping used for training

• Training/evaluation sessions lengthy/drilled,not rewarded if made mistakes

‣ One chimpanzee from four managed to learn the system

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• Sarah – Chimpanzee (Premack, 1971) cont.

• Vocabulary

‣ Learnt over 100 symbols denoting colours, shapes, sizes and logical relationships such as same/different and if … then …

• Combination

‣ Could understand complex instructions (e.g. six symbols)but did not create own equivalents

• Grammar

‣ Could learn that strict order of symbols important for following instructions or obtaining reinforcement

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• Sarah – Chimpanzee (Premack, 1971) cont.


• Able to follow complex instructions

IF APPLE THEN CHOCOLATE (take apple to get chocolate)SARAH INSERT BANANA PAIL APPLE DISHQUERY CUP EQUAL SPOON

‣ Displacement: told BROWN IS COLOUR OF CHOCOLATE,pointed to brown patch, no chocolate in view

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• Lana – Chimpanzee (Rumbaugh)

• Teaching

• Giant computer keyboard, coloured shapes stood for words

• Request food and drink, communicate with a trainer

• Shaping used in an attempt to teach grammar

• Grammar

‣ Learnt grammar poorly, trial & error was main strategy,many retries, eventually rote learning

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• Lana – Chimpanzee (Rumbaugh) cont.


‣ Generalised: MORE initially used inspecific instances, then use spread

‣ Creativity: cucumber named BANANA WHICH IS GREEN

• Culture

‣ Collaboration: other chimpanzees learnt to use system, Austin and Sherman could use keyboard to request tools from each other for problem solving tasks

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• Kanzi – Bonobo (Savage-Rumbaugh, 1990)

• Teaching

• Miniature version of computer keyboard,coloured shapes stood for words

• No initial training, began spontaneous use of single symbols after observing two years of failed attempts to train mother

• Training necessary after that to reinforce grammar etc.

• Vocabulary

‣ Over 150 symbols

• Grammar

‣ Eventually could demonstrate some evidence of learning

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• Kanzi – Bonobo (Savage-Rumbaugh, 1990) cont.


‣ If pressed a key for an object, and givena choice, only took named object

‣ Speech comprehension good, could follow spoken instructions; claimed to be equivalent to 2½ year old human

➡ Claimed to be the biggest success to date

“ape at the brink of the human mind”

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• Interim evaluation: Artificial language

• Wallman (1992)

• How much did Sarah understand thatthe symbols had underlying meaning?

(1) Sessions too narrow, repetitive single formats, slot filling

• e.g. SARAH GIVE MARY _____

➡ Most symbols redundant, simple association task

(2) Painstaking training, step by step, learning/combining

• SARAH INSERT BANANA PAIL APPLE DISH

➡ Step by step not needed if genuine understanding?

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• Interim evaluation: Artificial language cont.

• Wallman (1992) cont.

• Apes are good at learning to learn (see Lecture 7)

• Apes learnt to respond in certain ways tocertain sequences of shapes to receive rewards

➡ Artificial language projects look more extensivelogic/learning tasks than communication training

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Language or Problem Solving Training?

• Patterson

“language is no longer the exclusive domain of man”

• Pinker

“the chimps are highly trained animal acts”

• Clear, repeated pattern of findings

• Developmental reaches 2½ year old human, then stops

• Around 150 symbols learnt

• Grammatical rules learnt only with great difficulty

• Longer sequences give emphasis rather than information

• Not clear that concept of meaning is ever acquired

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• What is the language learning significance of 2½ years?

• Humans: threshold beyond which learning accelerates

• Apes: developmental ceiling, progression stops

• Lower cognitive capacity than humans

• Unlikely to have specialised short term verbal memory

➡ Language learning and use is a very hard task for apes

• Grammatical rules hard to identify and learn,compare with higher order logic tasks in Lecture 7

• Sequencing of long word strings difficult, requires cognitive capacity to combine multiple ideas

➡ Cognitive problems for apes stack up insurmountably

➡ Point where language enhances capacity never reached

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• What do apes understand when they use symbols?

• Creativity implies knowledge of underlying meaning?

‣ But ape creations rare/anecdotal/accidental

➡ Insufficient data to show that meanings of symbols are fully understood

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• What do apes understand when they use symbols? cont.

• Humans ascribing symbol meanings on behalf of apes?

• Key pressed by Lana to commence requests is named “please” by researchers

• Repetitive slot filling more like areasoning task than language?

• Lana could request an object (e.g, banana) but great difficulty when asked its name

• Lengthy training required before theconcept of name was understood

➡ Savage-Rumbaugh et.al. (1983)apes understand few, if any, symbols

➡ If no concept of meaning, how are symbols being used?

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• Symbols as concepts, or symbols as tools?

• Savage-Rumbaugh (1987)

• Apes are inappropriately taught

• Apple out of reach, must request apple to obtain it

➡ Ambiguous: symbol for an apple could mean:

Shape that is equivalent to apple: CONCEPTShape that, if chosen, results in apple: TOOL

➡ Understanding underlying concept of meaning is cognitively demanding?

➡ Conversely, chimpanzees known to be adept tool users

➡ Learning the consequence of using a symbol isnot the same as learning the meaning of a symbol

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• Symbols as concepts, or symbols as tools? cont.

• What do apes ‘talk‘ about?

• Language use as a method to obtain food andgratification dominates massively, even for Kanzi

➡ Language = communicative method for obtaining rewards

• Symbols rarely used for informational purposes,to discuss objects, or simply for the sake of it

➡ Lack of human-like interest in language itself

➡ Indicates something more profound than apes simply learning to use tools to play the laboratory game

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• Symbols as concepts, or symbols as tools? cont.

• Human cognitive capacity focused towards meaning

• Chimpanzee cognitive capacity focused towards use [at the expense of meaning]

Human: what is this?

Chimpanzee: what is the use of this?

• Good for learning how to use symbols as effective tools

• Bad for deeper-level understanding of language

➡ Chimpanzee focus detracts from cognitive capacity

• Exacerbates all language learning problems

• Causes the developmental glass ceiling

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➡ Language ability by apes in training studies exactlyas predicted from learning/problem solving research

➡ If anything, (mis)focused cognitive capacity detracts from ability, less effective learning than might be expected

➡ Insufficient learning to reach the point at which language yields cognitive enhancement fringe benefits

➡ No revealing of hidden untapped mental lives of apes

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Postscript: Teaching Other Animals

‣ Dogs able to learn verbal commands

‣ Dolphins and sea lions can learn torespond to a semaphore-like language

➡ Comprehending language easier than producing language

‣ Parrots (Pepperberg, 1990) more adept than chimpanzees in many ways

➡ Cognitive capacity focused towards word-sounds,enhances performance beyond expectations

• See Pearce (2008), Reznikova (2007)

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9.4 What Does Communication Reveal?

• Natural communication

➡ Animals who (perhaps) communicate symbolically do so with limited meaning, understanding, intentionality

• Taught communication

➡ Language learning exactly in line with general learning/ problem solving ability/(mis)focused cognitive capacity

➡ How much more is human language ability than high, focused cognitive capacity, and learning ability?

• In a social group, limited communicationpowers can still be used intelligently

➡ Look for animals exploiting their own strengths,not human strengths (Lecture 10)

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Major Sources

• Aitchison, J. (1989). The Articulate mammal (3rd edition). London: Unwin Hyman. [Any edition has the most important details]

• Pearce, J.M. (2008). Animal cognition & learning (3rd ed). Hove: Psychology Press.

• Pinker, S. (1994). The Language Instinct. London: Allen Lane.• Reznikova, Z. (2007). Animal intelligence. Cambridge: CUP.• Seyfarth, R.M., & Cheney, D.L. (2003). Signallers and receivers in

animal communication. Annual Review of Psychology, 54, 145-173.

• Wallman, J. (1992). Aping Language. Cambridge: CUP.

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References• Burghardt, G.M. (1985). Animal awareness: current perceptions and historical

perspective. American Psychologist, 40, 905-919.

• Cheney, D.L., & Seyfarth, R.M. (1985). Vervet monkey alarm calls: manipulation through shared information? Behaviour, 94, 150-166.

• Cheney, D.L., & Seyfarth, R.M. (1991). Reading minds or reading behaviour: tests for a theory of mind in monkeys. In A. Whiten (ed.). Natural Theories of Mind. Oxford: Blackwell.

• Cheney, D.L., & Seyfarth, R.M. (1992). Précis of how monkeys see the world. Behavioral and Brain Sciences, 15, 135-147.

• Gardner, R.A., & Gardner, B.T. (1969). Teaching sign language to a chimpanzee. Science, 165, 664-672.

• Gottfredson, L.S. (2007). Innovation, fatal accidents, and the evolution of general intelligence. In M. J. Roberts (Ed.), Integrating the mind. Hove: Psychology Press.

• Meo, M., Roberts, M.J., & Marucci, F. (2007). Element salience as a predictor of item difficulty for Ravens Progressive Matrices. Intelligence, 35, 359-368.

• Miles, H.L.W. (1990). The cognitive foundations for reference in a signing orangutan. In S.T. Parker, & K.R. Gibson (eds.). Language and Intelligence in Monkeys and Apes. Cambridge: CUP.

• Pepperberg, I.M. (1990). Conceptual abilities of some non-primate species, with an emphasis on the African Grey parrot. In S.T. Parker, & K.R. Gibson (eds.). Language and Intelligence in Monkeys and Apes. Cambridge: CUP.

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References• Premack, D. (1971). Language in chimpanzee? Science, 172, 808-822.

• Savage-Rumbaugh, S. (1987). A new look at ape language: comprehension of vocal speech and syntax. In D.W. Ledger (ed.) Nebraska Symposium on Motivation (vol. 35). Lincoln NB.: University of Nebraska Press.

• Savage-Rumbaugh, S. (1990). Grammatical combination in Pan paniscus: processes of learning and invention in the evolution and development of language. In S.T. Parker, & K.R. Gibson (eds.). Language and Intelligence in Monkeys and Apes. Cambridge: CUP.

• Savage-Rumbaugh, S., Pate, J.L., Lawson, J., Smith, S.T., & Rosenbaum, S. (1983). Can a chimpanzee make a statement? Journal of Experimental Psychology (General), 112, 457-491.

• Sebeok, T.A., & Umiker-Sebeok, J. (1980). Speaking of Apes. New York: Plenum Press.

• Seidenburg, M.S., & Petitto, L.A. (1979). Signing behavior in apes: a critical review. Cognition, 7, 177-215.

• Seyfarth, R.M., Cheney, D.L., & Marler, P. (1982). Vervet monkey alarm calls: semantic communication in a free ranging primate. Animal Behaviour, 28, 1070-1094.

• Terrace, H.S. (1979). Nim. London: Eyre Methuen.

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Lecture 9: Animal Communication - Tube Map Central · Lecture 9: Animal Communication • 9.1 What is Communication? • The language debate • Communication and intelligence •